<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    .box1 {
      float: left;
      width: 200px;
      height: 400px;
      background-color: yellowgreen;
    }
    .box2 {
      position: absolute;
      height: 400px;
      background-color: skyblue;
    }
  </style>
</head>
<body>
  <!-- BFC不与float box重叠 -->
   <div class="box1"></div>
   <div class="box2"></div>
</body>
</html>